1. Field of the Invention
The present invention relates generally to semiconductor processing equipment. More particularly, the present invention relates to a gas ring for a pancake reactor and to a method for using the same.
2. Description of Related Art
As is well known to those of skill in the art, substrate processing typically involved the formation of one or more layers on substrates. Generally, substrates, e.g., silicon wafers, were placed on a susceptor in a semiconductor processing reactor. Process gas was introduced into the semiconductor processing reactor, and a layer was formed on the substrates from the process gas.
To insure uniformity in the characteristics of the substrates, it was important that the formed layer was uniform, e.g., in thickness, across the substrates. To enhance the uniformity of the formed layer, the susceptor upon which the substrates were placed was typically rotated within the semiconductor processing reactor.
Further, the flow characteristics of the process gas through the semiconductor processing reactor was important. Typically, gas injectors located in and extending from the bottom of the semiconductor processing reactor injected the process gas upwards towards the dome of the semiconductor processing reactor above the susceptor. The process gas was then drawn down and around the susceptor to exhaust ports also located in the bottom of the semiconductor processing reactor. Thus, the process gas flow through the semiconductor processing reactor was turbulent and recirculatory. Due to the turbulent and recirculatory flow of process gas, particulates located within the semiconductor processing reactor has a tendency to become dislodged and contaminated the substrates.
Further, since all of the process gas had to flow pass the edge of the susceptor to the exhaust ports located in the bottom of the semiconductor processing reactor, the deposited layer was generally thicker near the edge of the susceptor and thinner near the center of the susceptor.